Wide viewing angle liquid crystal display comprising at least one floating electrode in locations facing corresponding one or more pixel electrodes with liquid crystal layer therebetween

ABSTRACT

A liquid crystal display (LCD) device. In one embodiment, the LCD device includes a first substrate and a second substrate positioned apart from the first substrate, a liquid crystal layer positioned between the first substrate and the second substrate, and a plurality of pixels. Each pixel includes two or more first common electrodes and one or more pixel electrodes formed on the first substrate, where each of the one or more pixel electrodes is located between two of the two or more first common electrodes. Each pixel further includes one or more floating electrodes and/or two or more second electrodes formed on the second substrate in locations opposite corresponding ones of the one or more pixel electrodes and the two or more first common electrodes on the first substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a reissue of U.S. Pat. No. 7,924,385, issued Apr.12, 2011.

FIELD OF THE INVENTION

The present invention relates generally to a liquid crystal display(LCD) device, and more particularly to an LCD device that utilizesfloating electrode switching (FES) to improve image quality with viewingangle characteristic and light transmittance of display.

BACKGROUND OF THE INVENTION

Liquid crystal display (LCD) is commonly used as a display devicebecause of its capability of displaying images with good quality whileusing little power. An LCD apparatus includes an LCD panel formed withliquid crystal cells and pixel elements with each associating with acorresponding liquid crystal cell and having a liquid crystal capacitorand a storage capacitor, a thin film transistor (TFT) electricallycoupled with the liquid crystal capacitor and the storage capacitor.These pixel elements are substantially arranged in the form of a matrixhaving a number of pixel rows and a number of pixel columns. Typically,scanning signals are sequentially applied to the number of pixel rowsfor sequentially turning on the pixel elements row-by-row. When ascanning signal is applied to a pixel row to turn on corresponding TFTsof the pixel elements of a pixel row, source signals (image signals) forthe pixel row are simultaneously applied to the number of pixel columnsso as to charge the corresponding liquid crystal capacitor and storagecapacitor of the pixel row for aligning orientations of thecorresponding liquid crystal cells associated with the pixel row tocontrol light transmittance therethrough. By repeating the procedure forall pixel rows, all pixel elements are supplied with correspondingsource signals of the image signal, thereby displaying the image signalthereon.

Liquid crystal molecules have a definite orientational alignment as aresult of their long, thin shapes. The orientations of liquid crystalmolecules in liquid crystal cells of an LCD panel play a crucial role inthe transmittance of light therethrough. For example, in a twist nematicLCD, when the liquid crystal molecules are in its tilted orientation,light from the direction of incidence is subject to various differentindexes of reflection. Since the functionality of LCDs is based on thebirefringence effect, the transmittance of light will vary withdifferent viewing angles. Due to such differences in light transmission,optimum viewing of an LCD is limited within a narrow viewing angle. Thelimited viewing angle of LCDs is one of the major disadvantagesassociated with the LCDs and is a major factor in restrictingapplications of the LCDs.

Several approaches exist for increasing the viewing angles of LCDs, suchas in-plane switching (IPS), and fringe field switching (FFS). As shownin FIG. 9(a) an IPS mode LCD 910 has a structure that two pixelelectrodes 921 and a common electrode 929, both for driving liquidcrystal molecules 932, are formed on a first substrate 920 in parallel.When a voltage is applied to the pixel electrodes 921 and the commonelectrode 929, an electric field 937 is generated in-plane to thesurface of the first substrate 920. In the IPS mode LCD 910, a distance,L₁, defined between the common electrode 929 and the pixel electrode 921is about the same order as a cell gap, d₁, defined between the firstsubstrate 920 and the second substrate 940. The IPS mode LCD 920 has theadvantage of viewing angle that is wider than the conventional TN modeLCD. However, since the pixel and the common electrodes 921 and 929 aremade of opaque metal films, there is a limitation in aperture ratio andtransmittance of light 945. In addition, due to the planar electricfield structure, the IPS mode LCD inherently suffers from severe imagesticking.

In order to overcome the limitation of the IPS mode LCD in apertureratio and transmittance of light, an FFS mode LCD is introduced. In theFFS mode LCD 950, as shown in FIG. 9(b), a plurality of pixel electrodes961 and a common electrode 969 are made of transparent metal films, forexample, indium tin oxide metal films, thereby improving the apertureratio compared to the IPS mode LCD. Furthermore, a distance, L₂, definedbetween two pixel electrodes is narrower than that a cell gap, d₂,defined between the first substrate 970 and the second substrate 990.When a voltage is applied between the pixel electrodes 961 and 969, afringe field 981 is generated in a region of the cell gap adjacent tothe common and the pixel electrodes 961 and 969, liquid crystalmolecules 982 disposed within the region are all driven, therebyimproving the transmittance of light 995, comparing to the IPS mode LCD.

However, in the IPS mode LCD and the FFS mode LCD, no conductive metalfilms are formed on the second substrate for preventing distortion ofthe electric field generated by the pixel electrode and the commonelectrode on the first substrate. Usually, an ITO film is formed on theback side of the second substrate to protect the LCD from electro-staticdamage, which makes increase manufacture cost and material cost of acolor filter.

Therefore, a heretofore unaddressed need exists in the art to addressthe aforementioned deficiencies and inadequacies.

SUMMARY OF THE INVENTION

The present invention, in one aspect, relates to an LCD device. In oneembodiment, the LCD device has a first structure and a second structurepositioned apart to define a cell gap therebetween, and a liquid crystallayer positioned in the cell gap between the first structure and thesecond structure. In one embodiment, the liquid crystal layer comprisesnematic liquid crystals having a positive dielectric anisotropy. Theliquid crystals are selected such that a product of the refractive indexδ_(n) of the liquid crystals and the cell gap is in a range of about0.15-0.60 um.

The first structure includes a first substrate having a first surfaceand an opposite, second surface defining a body portion therebetween; aplurality of scanning lines spacing-regularly formed on the secondsurface of the first substrate along a first direction; an insulationlayer formed on the first substrate covering the plurality of scanninglines; a plurality of signal lines spacing-regularly formed on theinsulation layer crossing over the plurality of scanning lines along asecond direction that is substantially perpendicular to the firstdirection; a passivation layer formed on the insulation layer coveringthe plurality of signal lines thereon; a plurality of first commonelectrodes spacing-regularly formed on the passivation layer along thesecond direction; and a plurality of pixel electrodes spacing-regularlyformed on the passivation layer along the second direction, each pixelelectrode located between two neighboring first common electrodes.

In one embodiment, each pixel electrode and one of its two neighboringfirst common electrodes define a distance therebetween, which is greaterthan the cell gap.

In one embodiment, each of the plurality of first common electrodes islocated over a corresponding one of the plurality of date lines. Inanother embodiment, each pair of the plurality of first commonelectrodes is distantly located over a corresponding one of theplurality of date lines.

The second structure includes a second substrate having a first surfaceand an opposite, second surface defining a body portion therebetween; ablack matrix formed on the first surface of the second substrate in apredetermined pattern; a color filter layer formed on the remainingportion of the second substrate; an overcoat layer formed on the colorfilter layer and the black matrix; a plurality of second commonelectrodes spacing-regularly formed on the overcoat layer along thesecond direction; and a plurality of floating electrodesspacing-regularly formed on the overcoat layer along the seconddirection, each floating electrode located between two neighboringsecond common electrodes.

The first structure and the second structure are positioned relative toeach other such that a cell gap is defined therebetween; each of theplurality of floating electrodes in the second structure is positionedopposite a corresponding one of the plurality of pixel electrodes in thefirst structure; each of the plurality of second common electrodes inthe second structure is positioned opposite a corresponding one of theplurality of first common electrodes in the first structure, and theblack matrix in the second structure is positioned opposite theplurality of scanning lines and the plurality of signal lines in thefirst structure, respectively.

Each of the plurality of pixel electrodes, the plurality of floatingelectrodes, the plurality of first common electrodes and the pluralityof second common electrodes is formed of a transparent, conductivematerial including indium zinc oxide (IZO), amorphous indium tin oxide(ITO), poly ITO, or any combination of them, with a thickness in therange of about 0.01-3.0 μm.

In one embodiment, the first structure further comprises a firstalignment layer formed on the passivation layer covering the pluralityof pixel electrodes and the plurality of first common electrodesthereon, and wherein the second structure further comprises a secondalignment layer formed on the overcoat layer covering the plurality offloating electrodes and the plurality of second common electrodesthereon. Each of the first alignment layer and the second alignmentlayer is formed to have a rubbing axis with a pre-tilted angle in arange of about 0-10 degrees relative to the second direction so as toalign the liquid crystals to a desired direction.

Additionally, the LCD device further includes a polarizer formed on thefirst surface of the first substrate, the polarizer having a polarizingaxis in a first predetermined direction, the polarizing axis beingoptically related to the liquid crystal layer; and an analyzer formed onthe second surface of the second substrate, the analyzer having anabsorbing axis in a second predetermined direction, the absorbing axisbeing optically related to the polarizer. The polarizing axis of thepolarizer and the rubbing axis of the first alignment layer define anangle in a range of about 0-90 degrees, and wherein the polarizing axisof the polarizer is about 90 degrees relative to the absorbing axis ofthe analyzer.

In another aspect, the present invention relates to an LCD device. Inone embodiment, the LCD device includes a first substrate and a secondsubstrate positioned apart to define a cell gap therebetween; a liquidcrystal layer positioned in the cell gap between the first substrate andthe second substrate; a plurality of scanning lines formed on the firstsubstrate along a first direction and a plurality of signal lines formedon the first substrate crossing over the plurality of scanning linesalong a second direction that is perpendicular to the first direction;and a plurality of pixels.

Each pixel is defined between two neighboring scanning lines and twoneighboring signal lines crossing over the two neighboring scanninglines and comprises an insulation layer formed on the first substrate;two or more first common electrodes formed on the insulation layer alongthe second direction, two of the two or more first common electrodeslocated over the two neighboring signal lines, respectively; one or morepixel electrodes formed on the insulation layer between the two of thetwo or more first common electrodes along the second direction; a blackmatrix formed on the second substrate in locations opposite the twoneighboring scanning lines and the two neighboring signal lines crossingover the two neighboring scanning lines in the first substrate; a colorfilter layer formed on the second substrate in an area surrounded by theblack matrix; an overcoat layer formed on the black matrix and the colorfilter; and at least one of one or more floating electrodes and two ormore second electrodes formed on the overcoat layer along the seconddirection in locations opposite corresponding ones of the one or morepixel electrodes and the two or more first common electrodes in thefirst substrate.

Furthermore, each pixel includes a switch device electrically coupledwith the one or more pixel electrodes.

Moreover, each pixel includes a first alignment layer formed on thepassivation layer covering the plurality of pixel electrodes and theplurality of first common electrodes thereon; and a second alignmentlayer formed on the overcoat layer covering the plurality of floatingelectrodes and the plurality of second common electrodes thereon. Eachof the first alignment layer and the second alignment layer is formed tohave a rubbing axis with a pre-tilted angle in a range of about 0-10degrees relative to the second direction so as to align the liquidcrystals to a desired direction.

In one embodiment, the LCD device further includes a polarizer formed onan exterior surface of the first substrate, the polarizer having apolarizing axis in a first predetermined direction, the polarizing axisbeing optically related to the liquid crystal layer; and an analyzerformed on an exterior of the second substrate, the analyzer having anabsorbing axis in a second predetermined direction, the absorbing axisbeing optically related to the polarizer, where the polarizing axis ofthe polarizer and the rubbing axis of the first alignment layer definean angle in a range of about 0-90 degrees, and the polarizing axis ofthe polarizer is about 90 degrees relative to the absorbing axis of theanalyzer.

In one embodiment, the liquid crystal layer comprises nematic liquidcrystals having a positive dielectric anisotropy. The liquid crystalsare selected such that a product of the refractive index δ_(n) of theliquid crystals and the cell gap is in a range of about 0.15-0.60 um.

In yet another aspect, the present invention relates to an LCD device.In one embodiment, the LCD device includes a first substrate and asecond substrate positioned apart from the first substrate; a liquidcrystal layer positioned between the first substrate and the secondsubstrate; and a plurality of pixels. Each pixel has two or more firstcommon electrodes formed on the first substrate; one or more pixelelectrodes formed on the first substrate, each of the one or more pixelelectrodes located between two of the two or more first commonelectrodes; and at least one of one or more floating electrodes and twoor more second electrodes formed on the second substrate in locationsopposite corresponding ones of the one or more pixel electrodes and thetwo or more first common electrodes in the first substrate.

Each pixel further includes a switch device electrically coupled withthe one or more pixel electrodes. In one embodiment, each pixel may alsoincludes a first alignment layer formed on the plurality of pixelelectrodes and the plurality of first common electrodes thereon; and asecond alignment layer formed on the plurality of floating electrodesand the plurality of second common electrodes thereon. Each of the firstalignment layer and the second alignment layer is formed to have arubbing axis with a pre-tilted angle in a range of about 0-10 degreesrelative to the direction of the one or more pixel electrodes so as toalign the liquid crystals to a desired direction.

In a further aspect, the present invention relates to a liquid crystaldisplay (LCD) device. In one embodiment, the LCD has a first substrateand a second substrate positioned apart from the first substrate; aliquid crystal layer positioned between the first substrate and thesecond substrate; and a plurality of pixels. Each pixel includes two ormore first common electrodes formed on the first substrate; one or morepixel electrodes formed on the first substrate, each of the one or morepixel electrodes located between two of the two or more first commonelectrodes; and at least one floating electrode formed on the secondsubstrate in locations opposite corresponding one of the one or morepixel electrodes on the first substrate.

These and other aspects of the present invention will become apparentfrom the following description of the preferred embodiment taken inconjunction with the following drawings, although variations andmodifications therein may be affected without departing from the spiritand scope of the novel concepts of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate one or more embodiments of theinvention and, together with the written description, serve to explainthe principles of the invention. Wherever possible, the same referencenumbers are used throughout the drawings to refer to the same or likeelements of an embodiment, and wherein:

FIG. 1 shows schematically a cross-sectional view of an LCD deviceaccording to one embodiment of the present invention;

FIG. 2 shows schematically (a) and (b) light transmittance curves of anLCD device, and (c) and (d) cross-sectional views of the LCD deviceshowing an electric field generated in the liquid crystal layeraccording to one embodiment of the present invention;

FIG. 3 shows schematically (a) a plane view of an LCD device and (b) across-sectional view of the LCD device along line A-A′ according to oneembodiment of the present invention;

FIG. 4 shows schematically (a) a plane view of an LCD device and (b) across-sectional view of the LCD device along line A-A′ according toanother embodiment of the present invention;

FIG. 5 shows schematically (a) a plane view of an LCD device and (b) across-sectional view of the LCD device along line A-A′ according to yetanother embodiment of the present invention;

FIG. 6 shows schematically (a) a plane view of an LCD device and (b) across-sectional view of the LCD device along line A-A′ according to analternative embodiment of the present invention;

FIG. 7 shows schematically (a) a plane view of an LCD device and (b) across-sectional view of the LCD device along line A-A′ according to oneembodiment of the present invention;

FIG. 8 shows schematically fabricating processes (steps) (a)-(e) of anLCD device according to one embodiment of the present invention; and

FIG. 9 shows schematically a cross-sectional view of (a) in-planeswitching (IPS) and (b) fringe field switching (FFS) LCD devices.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is more particularly described in the followingexamples that are intended as illustrative only since numerousmodifications and variations therein will be apparent to those skilledin the art. Various embodiments of the invention are now described indetail. Referring to the drawings, like numbers indicate like componentsthroughout the views. As used in the description herein and throughoutthe claims that follow, the meaning of “a”, “an”, and “the” includesplural reference unless the context clearly dictates otherwise. Also, asused in the description herein and throughout the claims that follow,the meaning of “in” includes “in” and “on” unless the context clearlydictates otherwise.

The description will be made as to the embodiments of the presentinvention in conjunction with the accompanying drawings in FIGS. 1-8. Inaccordance with the purposes of this invention, as embodied and broadlydescribed herein, this invention, in one aspect, relates to an LCDdevice that utilizes floating electrode switching (FES) to improve imagequality with viewing angle characteristic and light transmittance ofdisplay.

Referring to FIG. 1, an LCD device 100 is schematically shown accordingto one embodiment of the present invention. In this exemplaryembodiment, the LCD device 100 includes a first structure 110 and asecond structure 120 positioned apart to define a cell gap, H,therebetween, and a liquid crystal layer 180 positioned in the cell gapH between the first structure 110 and the second structure 120.

The liquid crystal layer 180 is filled with liquid crystal molecules182. In one embodiment, the liquid crystals 182 include a liquid crystalmaterial having a positive dielectric anisotropy, such as twistednematic (TN) liquid crystals, for example. The liquid crystals 182 areselected such that a product of the refractive index δ_(n) of the liquidcrystals and the cell gap H is in a range of about 0.15-0.60 um.

The first structure 110 includes a first substrate 112, an insulationlayer 114, a passivation layer 116, a first alignment layer 118, aplurality of pixel electrodes 140, a plurality of common electrodes 150,a plurality of scanning lines (not shown) and a plurality of signallines 130.

The first substrate 112 has a first surface 112a and an opposite, secondsurface 112b defining a body portion 112c therebetween. The plurality ofscanning lines is spacing-regularly formed on the second surface 112b ofthe first substrate 112 along a first direction. The insulation layer114 is formed on the second surface 112b of the first substrate 112 tocover the plurality of scanning lines thereon. The plurality of signallines 130 are spacing-regularly formed on the insulation layer 114crossing over the plurality of scanning lines in a second direction thatis substantially perpendicular to the first direction. Accordingly, theplurality of scanning lines and the plurality of signal lines 130 areelectrically insulated by the insulation layer 114. On the insulationlayer 114, the passivation layer 116 is formed to cover the plurality ofsignal lines 130 thereon. The plurality of scanning lines and theplurality of signal lines 130 define a plurality of pixels therewith. Inone embodiment, the plurality of pixels is arranged in a matrix. Thefirst direction corresponds to the row direction of the pixel matrix,while the second direction corresponds to the column direction of thepixel matrix.

The plurality of first common electrodes 150 and the plurality of pixelelectrodes 140 are spacing-regularly formed on the passivation layer 116along the second direction, where each pixel electrode 140 is locatedbetween two neighboring first common electrodes 150, and each pair ofthe plurality of first common electrodes 150 is distantly located over acorresponding one of the plurality of date lines 130. In the exemplaryembodiment shown in FIG. 1, each pixel electrode 140 and one of its twoneighboring first common electrodes 150 define a distance, D,therebetween, which is greater than the cell gap H. As described below,the plurality of first common electrodes 150 can also be formed suchthat only a single common electrode is located over a corresponding oneof the plurality of date lines 130. According to embodiments of thepresent invention, the plurality of first common electrodes 150 and theplurality of pixel electrodes 140 are located in a single plane (thepassivation layer 116).

The insulation layer 112 is formed of an insulating material such assilicon nitride (SiNx), silicon oxide (SiOx) or silicon oxynitride(SiON), or the like. The passivation layer 116 is formed of SiNx, SiOx,SiON or organic insulating material such as polyimide, and has athickness in the range of about 0.1-10.0 μm.

Each of the plurality of pixel electrodes 140 and the plurality of firstcommon electrodes 150 is formed of a transparent, conductive materialincluding indium zinc oxide (IZO), amorphous indium tin oxide (ITO),poly ITO, or the like, with a thickness in the range of about 0.01-3.0μm. In one embodiment, the plurality of pixel electrodes 140 and theplurality of first common electrodes 150 are in a lattice shape.

The first alignment layer 118 is formed on the passivation layer 116 tocover the plurality of pixel electrodes 140 and the plurality of firstcommon electrodes 150 thereon. The first alignment layer 118 has arubbing axis with a pre-tilted angle in a range of about 0-10 degreesrelative to the second direction so as to align the liquid crystals to adesired direction initially.

Additionally, the first structure 110 also includes a plurality of TFTsas switching elements (not shown). Each TFT is formed between a scanningline and a signal line that crosses the scanning line. The TFT includesa channel layer formed on the scanning line, a source electrodeextending from the signal line and overlapped with one side of thechannel layer by a selected portion, and a drain electrode overlappedwith the other side of the channel layer by a selected portion andconnected to the pixel electrode.

The second structure 120 includes a second substrate 122, a color filterlayer 124, an overcoat layer 116, a second alignment layer 118, a blackmatrix 190, a plurality of floating electrodes 160, and a plurality ofsecond common electrodes 170.

The second substrate 122 has a first surface 122a and an opposite,second surface 122b defining a body portion 122c therebetween. The blackmatrix 190 is formed on the first surface 122a of the second substrate122 in a predetermined pattern. The color filter layer 124 is formed onthe remaining portion of the second substrate 122. The overcoat layer126 is formed on the color filter layer 124 and the black matrix 190.The plurality of second common electrodes 170 and the plurality offloating electrodes 160 are spacing-regularly formed on the overcoatlayer 126 along the second direction, where each floating electrode 160is located between two neighboring second common electrodes 170, andeach pair of the plurality of second common electrodes 170 is distantlylocated under a corresponding portion of the black matrix 190.

Each of the plurality of floating electrodes 160 and the plurality ofsecond common electrodes 170 is formed of a transparent, conductivematerial including IZO, amorphous ITO, poly ITO, or the like, with athickness in the range of about 0.01-3.0 μm. In one embodiment, theplurality of floating electrodes 160 and the plurality of second commonelectrodes 170 are in a lattice shape.

The second alignment layer 128 is formed on the overcoat layer 126 tocover the plurality of floating electrodes 160 and the plurality ofsecond common electrodes 170 thereon. The second alignment layer 128 hasa rubbing axis with a pretilted angle in a range of about 0-10 degreesrelative to the second direction so as to align the liquid crystals to adesired direction initially.

As shown in FIG. 1, the first structure 110 and the second structure 120are positioned relative to each other such that a cell gap H is definedtherebetween. Furthermore, each of the plurality of floating electrodes160 in the second structure 120 is positioned opposite a correspondingone of the plurality of pixel electrodes 140 in the first structure 110,and each of the plurality of second common electrodes 170 in the secondstructure 120 is positioned opposite a corresponding one of theplurality of first common electrodes 150 in the first structure 110.Moreover, the black matrix 190 in the second structure 120 is positionedopposite the plurality of scanning lines and the plurality of signallines 130 in the first structure 110.

Accordingly, a storage capacitor (not shown) is formed at an overlappedportion of the common electrode and the pixel electrodes. The storagecapacitor holds data signal at a desired voltage level during one frame.

Additionally, the LCD device 100 also includes a polarizer and ananalyzer (not shown). The polarizer is formed on the first surface 112aof the first substrate 112. The polarizer has a polarizing axis in afirst predetermined direction where the polarizing axis is opticallyrelated to the liquid crystal layer 180. The analyzer is formed on thesecond surface 122b of the second substrate 122. The analyzer has anabsorbing axis in a second predetermined direction, where the absorbingaxis is optically related to the polarizer. The polarizing axis of thepolarizer and the rubbing axis of the first alignment layer 118 definean angle in a range of about 0-90 degrees. The polarizing axis of thepolarizer is about 90 degrees relative to the absorbing axis of theanalyzer.

For such a configuration of the LCD device 100, when a signal voltage isapplied to one of the transparent pixel electrodes 140, the voltage atthe transparent pixel electrode 140 is coupled to the correspondingfloating electrode 160, because the capacitance between the pixelelectrode 140 and the floating electrode 160 is much larger than thecapacitance between the pixel electrode 140 and the common electrode 150(170). As a result, the liquid crystals 182 rotate according to anelectric filed generated in the liquid crystal layer 180. The field fordriving liquid crystals in the cell gap without dead zone is generatedby the pixel electrode, floating electrode and common electrodes.Accordingly, the LCD device 100 is capable of operating with very hightransmittance, wide viewing angle and fast response time.

FIG. 2(a) shows a dark state of light transmittance 284 from an LCDdevice, according to one embodiment of the present invention. The LCDdevice includes two first common electrodes 250 and a pixel electrode240 distantly formed on a first substrate 210, two second commonelectrodes 270 and a floating electrode 260 distantly formed on a secondsubstrate 220 that is positioned apart from the first substrate 210 todefine a cell gap (a liquid crystal layer) 280 therebetween that isfilled with liquid crystals 282. In the dark state, no electric field isgenerated in the liquid crystal layer 280. As a result, no lighttransmittance of light 284 is obtained from the LCD device. FIG. 2(b)shows a white state of light transmittance 286 from the LCD deviceshowing equal potential lines 285 formed within the liquid crystal layer280. Accordingly, the liquid crystals 282 can be oriented to desiredirections due to the induced electric field 285 in the liquid crystallayer 280. The corresponding light transmittance curve 286 of the LCDdevice 200 indicates that the light transmittance is obtained over thepixel in the white state.

Referring to FIG. 3, an LCD device 300 according to one embodiment ofthe present invention is schematically shown, where figure (a) is aplane view of a unit pixel of the LCD device 300 and figure (b) is across-sectional view of the LCD device 300 along line A-A′.

The LCD device 300 includes a first substrate 312, a gate insulatingfilm 314 formed on the first substrate 312, and a plurality of scanning(gate) lines 335 and data (signal) lines 330, respectively, formed tocross each other and insulated by the gate insulating film 314, therebydefining a plurality of pixel regions 301 where they cross. Theplurality of scanning lines 335 is formed along a first direction 391and plurality of signal lines 330 is formed along a second direction 393that is substantially perpendicular to the first direction 391.Additionally, a plurality of common bus lines 359 is also formed on thefirst substrate 312 with each common bus line 359 adjacent to acorresponding scanning line 335. A passivation layer 316 is formed onthe gate insulating film 314 to cover the plurality of signal lines 330.

Furthermore, the LCD device 300 includes a plurality of pixel electrodes341 and 343, and a plurality of first common electrodes 351, 353 and 355spacing-regularly and alternatively formed on the passivation layer 316.In this exemplary embodiment shown in FIG. 3, each pixel region 301includes two pixel electrodes 341 and 343 and three first commonelectrodes 351, 353 and 355. The first common electrodes 353 and 355 areformed on the passivation layer 316 in regions over the correspondingsignal line 330 and scanning line 335, respectively, while the firstcommon electrode 351 is formed between the first common electrodes 353and 355 on the passivation layer 316. The pixel electrode 341 is formedbetween the first common electrodes 353 and 351 on the passivation layer316, while the pixel electrode 343 is formed between the first commonelectrodes 351 and 355 on the passivation layer 316.

The pixel region 301 also includes a TFT 347. It is used as a switchingelement and formed between the gate line 335 and the signal line 330.For example, the TFT 347 includes a gate electrode extending from thegate line 335, a gate insulating film 314 formed on the gate electrode,a channel layer (not shown) formed on the gate insulating film 314 abovethe gate electrode, a source electrode extending from the signal line330 and overlapped with one side of the channel layer by a selectedportion, and a drain electrode overlapped with the other side of thechannel layer by a selected portion and connected to the pixelelectrodes 341 and 343. The TFT 347 is capable of transmitting signalsapplied to the signal line 330 to the pixel electrodes 341 and 343 inresponse to a signal applied to the gate line 335.

Furthermore, the LCD device 300 include a second substrate 322, a blackmatrix 390 formed on the second substrate 322 in a predeterminedpattern, a color filter film 324 formed on the remaining portion of thesecond substrate 322, an overcoat layer 326 formed on the black matrix390 and the color filter film 326, and a plurality of second commonelectrodes 371, 373 and 375, and a plurality of floating electrodes 371spacing-regularly and alternatively formed on the overcoat layer 326.

As shown in FIG. 3, each pixel region 301 includes two floatingelectrodes 361 and 363 and three second common electrodes 371, 373 and375. The second common electrodes 373 and 375 are formed on the overcoatlayer 326 in regions under the corresponding portion of the black matrix390, while the second common electrode 371 is formed between the secondcommon electrodes 373 and 375 on the overcoat layer 326. The floatingelectrode 361 is formed between the second common electrodes 373 and 371on the overcoat layer 326, while the floating electrode 363 is formedbetween the second common electrodes 371 and 375 on the overcoat layer326.

The second substrate 322 is positioned apart from the first substrate312 to define a cell gap therebetween for receiving a liquid crystallayer 380. Furthermore, the first substrate 312 and the second substrate322 are positioned relative to each other such that for each pixelregion 301, the floating electrodes 361 and 363 in the second substrate371 are positioned opposite the corresponding pixel electrodes 341 and342 in the first substrate 312, respectively. The second commonelectrodes 371, 373 and 375 in the second substrate 322 are positionedopposite the corresponding first common electrodes 351, 353 and 357 inthe first substrate 312, respectively. Additionally, the black matrix190 in the second substrate 322 is positioned opposite the correspondingscanning lines 335 and signal lines 130 in the first substrate 312.Accordingly, a storage capacitor 345 is formed at an overlapped portionof the common electrode and the pixel electrodes. The storage capacitor345 holds data signal at a desired voltage level during one frame.

FIG. 4-7 shows various embodiments of the LCD device 400, 500, 600 or700 according to the present invention. Each embodiment of the LCDdevice includes a unique configuration of common electrodes, pixelelectrodes and floating electrodes formed on the first and secondsubstrates.

For example, in the embodiment shown in FIG. 4, each pixel region 401has two pixel electrodes 441 and 443, and three first common electrodes451, 453 and 455 formed on the first structure 410, which are in a sameconfiguration as these in FIG. 3, and two floating electrodes 461 and462 and two second common electrodes 473 and 475 formed on a secondstructure 420. Comprising to the LCD device shown in FIG. 3, no secondcommon electrode is formed between the floating electrodes 461 and 463on the second substrate in the LCD device 400. For such a configuration,the LC efficiency (transmittance) of the LCD device 400 may be slightlylower than that of the LCD shown in FIG. 3. But it can reduce shortdefect between common electrodes and floating electrodes by fabricationprocess.

In the embodiment shown in FIG. 5, each pixel region 501 has threesecond common electrodes 571, 573 and 575 and no floating electrodeformed on a second structure 520. Similarly, such a configuration of theLCD device 500 may reduce slightly the LC efficiency (transmittance),comparing to the LCD shown in FIG. 3, but it can reduce short defectbetween common electrodes and floating electrodes by fabricationprocess.

In the embodiment shown in FIG. 6, each pixel region 601 has two firstcommon electrodes 653 and 655 and a pixel electrode 641 formed on thefirst structure 610, and two second common electrodes 673 and 675 and afloating electrode 661 formed on a second structure 620. The pixelelectrode 641 is located between two first common electrodes 653 and655, while the floating electrode 661 is located between two secondcommon electrodes 673 and 675. In the embodiment, the aperture ratio ofpixels is improved, but driving voltage is little higher than that ofthe LCD device shown in FIG. 3.

The LCD device shown in FIG. 7 is same as that of FIG. 1, where in eachpixel region 701, a pixel electrode 741 and two pairs of first commonelectrodes 753 and 755 formed on the first structure 710, a floatingelectrode 761 and two second common electrodes 773 and 775 formed on thesecond structure 720. Each pair of the first and second commonelectrodes is located in a region over a corresponding signal line.Accordingly, it can reduce RC delay of signal line by reducing ofoverlap capacitance between common electrodes and signal electrodes, butit may increase signal noise to pixel electrodes.

Referring now to FIG. 8, a method 800 of fabricating the invented LCDdevice is schematically shown according to one embodiment of the presentinvention. The method includes the following steps. At first, a firstsubstrate 810 is provided. The first substrate 810 is formed of glass,or the likes. Then, a plurality of gate electrodes 820 electricallycoupled to a gate line is formed spatially apart from one another on thefirst substrate 810. Each pair of adjacent gate electrodes 820 defininga pixel area 801 and a capacitor area 802 therebetween, where the pixelarea 801 is adjacent to a switching area 812 in which a correspondinggate electrode 820 is formed, as shown in FIG. 8(a). The gate electrode820 is formed of a metal such as aluminum (Al), molybdenum (Mo),chromium (Cr), tantalum (Ta), copper (Cu), multilayer or alloy.

A dielectric layer (gate insulation film) 830 is formed on the firstsubstrate 810 and the plurality of gate electrodes 820. The gateinsulation film 830 is formed of SiNx, SiOx, or SiON. In one embodiment,the gate insulation film 830 is formed in such a manner that SiNx orSiOx is deposited on the first substrate 810 and the plurality of gateelectrodes 820 by plasma enhancement chemical vapor deposition (PECVD).

A semiconductor layer 840 is then formed on the gate insulation film 830in each switching area 812. Subsequently, a contact layer 845 is formedon the semiconductor layer 840 and patterned to have a first contactportion 842 and a second contact portion 844 separated from the firstcontact portion 842, as shown in FIG. 8(b). The semiconductor layer 840comprises an amorphous silicon or a poly silicon, or the likes. Thecontact layer 845 is formed of a doped amorphous silicon such as n⁺doped a-Si or p⁺ doped a-Si. In one embodiment, the semiconductor layer840 and the contact layer 845 are formed in such a manner that theamorphous silicon (a-Si) and the doped amorphous silicon (n⁺ doped a-Sior p⁺ doped a-Si) are successively deposited by PECVD and thenpatterned.

Alternatively, the gate insulation film 830 of SiNx or SiOx, theamorphous silicon layer 840, and the doped amorphous silicon layer 845may sequentially be deposited, and the amorphous silicon layer 840 andthe doped amorphous silicon layer 845 may be patterned to form thesemiconductor layer 840 and the contact layer 845.

Afterwards, a metal layer 860 is formed on the semiconductor layer 840and the contact layer 845 in each switching area 812. The metal layer860 is patterned to have a first portion 862 that is connected to asignal line and a second portion 864 that is separated from the firstportion 862 and connected to the first pixel electrode layer 850 in acorresponding pixel area 801, as shown in FIG. 8(c).

As shown in FIG. 8(d), a passivation layer (film) 870 is then formed ofa dielectric material such as SiNx or SiOx on the metal layer 860 ineach switching area 812 and each pixel area 801, which defines a viahole for coupling the switching device with the pixel electrode.

The next step, as shown in FIG. 8(e), is to form one or more pixelelectrodes 880 and two or more first common electrodes 850, 890 on thepassivation layer 870 in each pixel area 801, which are formed of atransparent, conductive material including IZO, amorphous ITO, poly ITO,or the like, with a thickness in the range of about 0.01-3.0 μm.

Additionally, the method further includes the steps of providing asecond substrate facing the first substrate and forming two or moresecond common electrodes and/or one or more floating electrodes on thesecond substrate. The liquid crystals are injected into the liquidcrystal layer defined between the first substrate and the secondsubstrate. The liquid crystals have a positive dielectric anisotropy.

The present invention, among other things, discloses an LCD device thatutilizes the FES to improve image quality with viewing anglecharacteristic and light transmittance of display. According to theembodiments of the present invention, the LCD device has a plurality oftransparent first common electrodes and pixel electrodes formed on afirst substrate, and a plurality of second transparent common electrodesand/or floating electrodes formed on a second substrate secondsubstrate, where the first substrate and the second substrate arepositioned relative to each other such that each second transparentcommon electrode on the second substrate is opposite a correspondingtransparent first common electrodes on a first substrate, and eachfloating electrode on the second substrate second substrate is oppositea corresponding pixel electrode on the first substrate.

The foregoing description of the exemplary embodiments of the inventionhas been presented only for the purposes of illustration and descriptionand is not intended to be exhaustive or to limit the invention to theprecise forms disclosed. Many modifications and variations are possiblein light of the above teaching.

The embodiments were chosen and described in order to explain theprinciples of the invention and their practical application so as toactivate others skilled in the art to utilize the invention and variousembodiments and with various modifications as are suited to theparticular use contemplated. Alternative embodiments will becomeapparent to those skilled in the art to which the present inventionpertains without departing from its spirit and scope. Accordingly, thescope of the present invention is defined by the appended claims ratherthan the foregoing description and the exemplary embodiments describedtherein.

What is claimed is:
 1. A liquid crystal display (LCD) device, comprising: a. a first structure comprising: i. a first substrate having a first surface and an opposite, second surface defining a body portion therebetween; ii. a plurality of scanning lines regularly spaced and formed on the second surface of the first substrate along a first direction; iii. an insulation layer formed on the first substrate covering the plurality of scanning lines; iv. a plurality of signal lines regularly spaced and formed on the insulation layer crossing over the plurality of scanning lines along a second direction that is substantially perpendicular to the first direction; v. a passivation layer formed on the insulation layer covering the plurality of signal lines thereon; vi. a plurality of first common electrodes regularly spaced and formed on the passivation layer along the second direction; and vii. a plurality of pixel electrodes regularly spaced and formed on the passivation layer along the second direction, each of the pixel electrodes located between two neighboring first common electrodes; b. a second structure comprising: i. a second substrate having a first surface and an opposite, second surface defining a body portion therebetween; ii. a black matrix formed on the first surface of the second substrate directly facing the plurality of scanning lines and the plurality of signal lines in the first structure; iii. a color filter layer formed on the remaining portion of the second substrate; iv. an overcoat layer formed on the color filter layer and the black matrix; v. a plurality of second common electrodes regularly spaced and formed on the overcoat layer along the second direction, each of the plurality of second common electrodes directly facing a corresponding one of the plurality of first common electrodes on the first substrate; and vi. a plurality of floating electrodes regularly spaced and formed on the overcoat layer on the second substrate along the second direction, each of the plurality of floating electrodes directly facing a corresponding one of the plurality of pixel electrodes on the first substrate; wherein the first structure and the second structure are positioned relative to each other such that a cell gap is defined therebetween; and c. a liquid crystal layer having a plurality of liquid crystal molecules, the liquid crystal layer being positioned in the cell gap between the first structure and the second structure; wherein each of the plurality of floating electrodes is electrically disconnected from floating and is not directly electrically connected to the pixel electrodes, the first common electrodes, and the second common electrodes, such that, when a signal voltage is applied to a pixel electrode, the voltage is coupled to a corresponding floating electrode via the capacitance between the pixel electrode and the floating electrode, thereby inducing an electric field in the liquid crystal layer in the region between the pixel electrode, the floating electrode, the first common electrodes and the second common electrodes, and wherein the liquid crystal molecules in the region are rotated according to the electric field.
 2. The LCD device of claim 1, wherein the liquid crystal layer comprises nematic liquid crystals having a positive dielectric anisotropy.
 3. The LCD device of claim 2, wherein the liquid crystals are selected such that a product of the refractive index δ_(n) of the liquid crystals and the cell gap is in a range of about 0.15-0.60 μm.
 4. The LCD device of claim 1, wherein each of the pixels electrode and one of its two neighboring first common electrodes define a distance therebetween, which is greater than the cell gap.
 5. The LCD device of claim 1, wherein the first structure further comprises a first alignment layer formed on the passivation layer covering the plurality of pixel electrodes and the plurality of first common electrodes thereon, and wherein the second structure further comprises a second alignment layer formed on the overcoat layer covering the plurality of floating electrodes and the plurality of second common electrodes thereon.
 6. The LCD device of claim 5, wherein each of the first alignment layer and the second alignment layer is formed to have a rubbing axis with a pre-tilted angle in a range of about 0-10 degrees relative to the second direction so as to align the liquid crystals to a desired direction.
 7. The LCD device of claim 6, further comprising: a. a polarizer formed on the first surface of the first substrate, the polarizer having a polarizing axis in a first predetermined direction, the polarizing axis being optically related to the liquid crystal layer; and b. an analyzer formed on the second surface of the second substrate, the analyzer having an absorbing axis in a second predetermined direction, the absorbing axis being optically related to the polarizer.
 8. The LCD device of claim 7, wherein the polarizing axis of the polarizer and the rubbing axis of the first alignment layer define an angle in a range of about 0-90 degrees, and wherein the polarizing axis of the polarizer is about 90 degrees relative to the absorbing axis of the analyzer.
 9. The LCD device of claim 1, wherein each of the plurality of first common electrodes is located over a corresponding one of the plurality of signal lines.
 10. The LCD device of claim 1, wherein each pair of the plurality of first common electrodes is distantly located over a corresponding one of the plurality of signal lines.
 11. The LCD device of claim 1, wherein each of the plurality of pixel electrodes, the plurality of floating electrodes, the plurality of first common electrodes and the plurality of second common electrodes is formed of a transparent, conductive material including indium zinc oxide (IZO), amorphous indium tin oxide (ITO), poly ITO, or any combination of them, with a thickness in the range of about 0.01-3.0 μm.
 12. A liquid crystal display (LCD) device, comprising: a. a first substrate and a second substrate positioned apart to define a cell gap therebetween; b. a liquid crystal layer having a plurality of liquid crystal molecules, the liquid crystal layer being positioned in the cell gap between the first substrate and the second substrate; c. a plurality of scanning lines formed on the first substrate along a first direction and a plurality of signal lines formed on the first substrate crossing over the plurality of scanning lines along a second direction that is perpendicular to the first direction; and d. a plurality of pixels, each of the pixels being defined between two neighboring scanning lines and two neighboring signal lines crossing over the two neighboring scanning lines and comprising: i. an insulation layer formed on the first substrate; ii. two or more first common electrodes formed on the insulation layer along the second direction, two of the two or more first common electrodes located over the two neighboring signal lines, respectively; iii. one or more pixel electrodes formed on the insulation layer between the two of the two or more first common electrodes along the second direction; iv. a black matrix formed on the second substrate in locations directly facing the two neighboring scanning lines and the two neighboring signal lines crossing over the two neighboring scanning lines in the first substrate; v. a color filter layer formed on the second substrate in an area surrounded by the black matrix; vi. an overcoat layer formed on the black matrix and the color filter; vii. two or more second common electrodes formed on the overcoat layer along the second direction, the two or more second common electrodes directly facing corresponding two or more first common electrodes on the first substrate; and viii. at least one of one or more floating electrodes formed on the overcoat layer on the second substrate along the second direction in locations directly facing corresponding ones of the one or more pixel electrodes formed on the first substrate; wherein the at least one of one or more floating electrodes is electrically disconnected from floating and is not directly electrically connected to the pixel electrodes, the first common electrodes, and the second common electrodes, such that, when a signal voltage is applied to a pixel electrode, the voltage is coupled to a corresponding floating electrode via the capacitance between the pixel electrode and the floating electrode, thereby inducing an electric field in the liquid crystal layer in the region between the pixel electrode, the floating electrode, the first common electrodes and the second common electrodes, and wherein the liquid crystal molecules in the region are rotated according to the electric field.
 13. The LCD device of claim 12, wherein the liquid crystal layer comprises nematic liquid crystals having a positive dielectric anisotropy.
 14. The LCD device of claim 13, wherein the liquid crystals are selected such that a product of the refractive index δ_(n) of the liquid crystals and the cell gap is in a range of about 0.15-0.60 μm.
 15. The LCD device of claim 12, wherein each of the pixels further comprises a switch device electrically coupled with the one or more pixel electrodes.
 16. The LCD device of claim 12, wherein each of the pixels further comprises: a. a first alignment layer formed on the passivation layer covering the plurality of pixel electrodes and the plurality of first common electrodes thereon; and b. a second alignment layer formed on the overcoat layer covering the plurality of floating electrodes and the plurality of second common electrodes thereon.
 17. The LCD device of claim 16, wherein each of the first alignment layer and the second alignment layer is formed to have a rubbing axis with a pre-tilted angle in a range of about 0-10 degrees relative to the second direction so as to align the liquid crystals to a desired direction.
 18. The LCD device of claim 17, further comprising: a. a polarizer formed on an exterior surface of the first substrate, the polarizer having a polarizing axis in a first predetermined direction, the polarizing axis being optically related to the liquid crystal layer; and b. an analyzer formed on an exterior of the second substrate, the analyzer having an absorbing axis in a second predetermined direction, the absorbing axis being optically related to the polarizer.
 19. The LCD device of claim 18, wherein the polarizing axis of the polarizer and the rubbing axis of the first alignment layer define an angle in a range of about 0-90 degrees, and wherein the polarizing axis of the polarizer is about 90 degrees relative to the absorbing axis of the analyzer.
 20. A liquid crystal display (LCD) device, comprising: a. a first substrate and a second substrate positioned apart from the first substrate; b. a liquid crystal layer having a plurality of liquid crystal molecules, the liquid crystal layer being positioned between the first substrate and the second substrate; and c. a plurality of pixels, each of the pixels comprising: i. two or more first common electrodes formed on the first substrate; ii. one or more pixel electrodes formed on the first substrate, each of the one or more pixel electrodes located between two of the two or more first common electrodes; iii. two or more second common electrodes formed on the second substrate in locations directly facing corresponding ones of the two or more first common electrodes on the first substrate; and iv. at least one of one or more floating electrodes formed on the second substrate in locations directly facing corresponding ones of the one or more pixel electrodes on the first substrate; wherein the at least one of one or more floating electrodes is electrically disconnected from floating and is not directly electrically connected to the pixel electrodes, the first common electrodes, and the second common electrodes, such that, when a signal voltage is applied to a pixel electrode, the voltage is coupled to a corresponding floating electrode via the capacitance between the pixel electrode and the floating electrode, thereby inducing an electric field in the liquid crystal layer in the region between the pixel electrode, the floating electrode, the first common electrodes and the second common electrodes, and wherein the liquid crystal molecules in the region are rotated according to the electric field.
 21. The LCD device of claim 20, wherein the liquid crystal layer comprises nematic liquid crystals having a positive dielectric anisotropy.
 22. The LCD device of claim 20, wherein each of the pixels further comprises a switch device electrically coupled with the one or more pixel electrodes.
 23. The LCD device of claim 20, wherein each of the pixels further comprises: a. a first alignment layer formed on the plurality of pixel electrodes and the plurality of first common electrodes thereon; and b. a second alignment layer formed on the plurality of floating electrodes and the plurality of second common electrodes thereon.
 24. The LCD device of claim 23, wherein each of the first alignment layer and the second alignment layer is formed to have a rubbing axis with a pre-tilted angle in a range of about 0-10 degrees relative to the direction of the one or more pixel electrodes so as to align the liquid crystals to a desired direction.
 25. A liquid crystal display (LCD) device, comprising: a. a first substrate and a second substrate positioned apart from the first substrate; b. a liquid crystal layer positioned between the first substrate and the second substrate, the liquid crystal layer having a plurality of liquid crystal molecules; and c. a plurality of pixels, each of the pixels comprising: i. two or more first common electrodes formed on the first substrate; ii. one or more pixel electrodes formed on the first substrate, each of the one or more pixel electrodes located between two of the two or more first common electrodes; iii. two or more second common electrodes formed on the second substrate in locations directly facing corresponding ones of the two or more first common electrodes on the first substrate; and iv. at least one floating electrode formed on the second substrate in locations directly facing a corresponding one of the one or more pixel electrodes on the first substrate; wherein the at least one floating electrode is electrically disconnected from floating and is not directly electrically connected to the pixel electrodes, the first common electrodes, and the second common electrodes, such that, when a signal voltage is applied to a pixel electrode, the voltage is coupled to a corresponding floating electrode via the capacitance between the pixel electrode and the floating electrode, thereby inducing an electric field in the liquid crystal layer in the region between the pixel electrode, the floating electrode, the first common electrodes and the second common electrodes, and wherein the liquid crystal molecules in the region are rotated according to the electric field. 